1. Field of the Invention
The present invention relates to an ink-jet recording head that jets ink particles through nozzle holes by applying pressure to the ink contained in pressure chambers by pressure producing elements.
2. Description of the Related Art
Generally, an ink-jet recording head includes an ink reservoir connected to an external ink tank, a plurality of pressure chambers communicating with the ink reservoir by means of ink inlets, pressure producing elements, such as piezoelectric vibrators or heating means, and a nozzle plate provided with nozzle holes through which the ink is jetted in ink particles.
FIG. 10 is a vertical sectional view of a conventional ink-jet recording head provided with longitudinal oscillation mode piezoelectric vibrators and FIG. 11 is a cross-sectional view taken on line Axe2x80x94A in FIG. 10.
Referring to FIG. 10, a conventional ink-jet recording head includes a passage forming plate 60, a nozzle plate 61 disposed on the front surface 60a of the passage plate 60, a casing member 62 disposed on the back surface 60b of the passage plate 60, and a sealing plate 63 held between the back surface 60b of the passage plate 60 and the casing member 62.
A plurality of pressure chambers 64 are formed in the passage forming plate 60. A plurality of nozzle holes 65 communicating with the pressure chambers 64, respectively, are formed in the nozzle plate 61. An ink reservoir 66 for containing ink to be supplied to the pressure chambers 64 is formed in the passage forming plate 60. The pressure chambers communicate with the ink reservoir 66 by means of ink inlets 67, respectively. The ink inlets 67 adjust the flow of the ink into the pressure chambers 64. The sealing plate 63 is attached hermetically to the back surface of the passage forming plate 60 to close the open back ends of the pressure chambers 64, the ink inlets 67 and the ink reservoir 66.
A plurality of piezoelectric vibrators 68 are housed in the casing member 62 so as to correspond to the plurality of pressure chambers 64, respectively. The piezoelectric vibrators 68 are held fixedly by a holding member 69 on the casing member 62.
The sealing plate 63 has a thick part 71 including a plurality of lands 70 connected to the plurality of piezoelectric vibrators 68, respectively, and a thin part 73 including elastically deformable parts 72 surrounding the lands 70, respectively. As shown in FIGS. 10 and 11, the thin part 73 is provided with a thin compliant part 74 of a shape substantially resembling that of the ink reservoir 66. An ink supply pipe 75 carries the ink into the ink reservoir 66. The ink supply pipe 75 penetrates the sealing plate 63 and opens into the ink reservoir 66. the ink supply pipe 75 is connected to a middle part of the elongate ink reservoir 66 in order that the ink supplied into the ink reservoir 66 is able to flow through the shortest possible distance to the extremities of the ink reservoir 66 and resistance against the flow of the ink is reduced to the least possible extent.
In this conventional ink-jet recording head, the sealing plate 63 must provide a part through which the ink supply pipe 75 extends and hence the thin compliant part 74 has a break in a middle part thereof, which affects adversely to the compliance of the compliant part 74.
Since the ink reservoir 66 is formed in the passage forming plate 60, the depth of the ink reservoir 66 cannot exceed the thickness of the passage forming plate 60. Therefore, if the ink-jet recording head is provided with a large number of nozzles and has a big length and the ink reservoir 66 has a big length, the width of the ink reservoir 66 needs to be increased to reduce resistance against the flow of the ink flowing toward the extremities of the ink reservoir 66. Consequently, the size of the ink-jet recording head is inevitably large.
The present invention has been made in view of the aforesaid problems and it is therefore an object of the present invention to provide an ink-jet recording head having high compliance and capable of being formed in a small size.
According to the present invention, an ink-jet recording head comprises: a passage forming plate provided with a plurality of pressure chambers; a nozzle plate disposed on one surface of the passage forming plate and provided with a plurality of nozzle holes respectively communicating with the plurality of pressure chambers; a plurality of pressure producing elements for applying pressure to ink contained in the plurality of pressure chambers; a casing member disposed on a side of the other surface of the passage forming plate and provided with an ink reservoir for containing the ink to be supplied to the plurality of pressure chambers; and a sealing plate disposed between the other surface of the passage forming plate and the casing member and connected to the plurality of pressure producing elements; wherein the sealing plate is provided with a plurality of through holes respectively communicating with both the plurality of pressure chambers and the ink reservoir.
Preferably, the plurality of through holes connected to the ink reservoir via a plurality of ink inlets, respectively, and wherein the ink inlets are capable of adjusting flow of ink between the ink reservoir and the pressure chambers.
Preferably, the sealing plate has a thick part including a plurality of lands connected to the piezoelectric vibrators, respectively, and a thin part including elastic parts capable elastic deformation and surrounding the lands.
Preferably, the plurality of ink inlets are formed in the thin part of the sealing plate.
Preferably, the sealing plate is formed by laminating a metal sheet and a polymer film, and the elastic parts are formed in the polymer film.
Preferably, the plurality of ink inlets are formed by etching the metal sheet.
Preferably, the plurality of through holes are formed by laser-machining portions of the polymer film corresponding to etched parts of the metal sheet.
Preferably, the sealing plate is formed by processing a plate member which can be elastically deformable at least by thinning.
Preferably, the plate member is a metal sheet, and the plurality of through holes are formed in the metal sheet by subjecting the metal sheet to press working.
Preferably, the plate member is a metal sheet, and the plurality of through holes are formed by etching the metal sheet.
Preferably, the plurality of ink inlets are recesses formed in a surface, which faces the sealing plate, of the casing member.
Preferably, the plurality of through holes are capable of adjusting flow of ink between the ink reservoir and the pressure chambers.
Preferably, the sealing plate has a thick part including a plurality of lands connected to the piezoelectric vibrators, respectively, and a thin part including elastic parts capable elastic deformation and surrounding the lands.
Preferably, the sealing plate is formed by laminating a metal sheet and a polymer film, and the elastic parts are formed in the polymer film.
Preferably, the plurality of through holes are formed by subjecting the sealing plate to press working.
Preferably, the plurality of through holes are formed by etching the metal sheet and laser-machining the polymer film.
Preferably, the sealing plate is formed by processing a plate member which can be elastically deformable at least by thinning.
Preferably, the plate member is a metal sheet, and the plurality of through holes are formed in the metal sheet by subjecting the metal sheet to press working.
Preferably, the plate member is a metal sheet, and the plurality of through holes are formed by etching the metal sheet.
Preferably, the ink reservoir has an outlet opening opened in a surface, which faces the sealing plate, of the casing member, a compliant part is formed in a part, corresponding to the outlet opening of the ink reservoir, of the sealing plate, and a compliance space is formed in a part of the passage forming plate corresponding to the compliant part to enable the compliant part to deform.
Preferably, the compliance space is opened to atmosphere.
Preferably, the ink reservoir has opposite end parts with respect to a direction in which the plurality of pressure chambers are arranged, and the opposite end parts have width decreasing toward their extremities.
Preferably, the ink reservoir has opposite end parts with respect to a direction in which the plurality pressure chambers are arranged, and depth of the opposite end parts decreases toward their extremities.
Preferably, the passage forming plate is a metal plate, and the plurality of pressure chambers are formed in the metal plate by press working.